#include <event2/listener.h>
#include <event2/bufferevent.h>
#include <event2/buffer.h>

#include <arpa/inet.h>

#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>

static void
echo_read_cb(struct bufferevent *bev, void *ctx)
{
	/* This callback is invoked when there is data to read on bev. */
	struct evbuffer *input = bufferevent_get_input(bev);
	struct evbuffer *output = bufferevent_get_output(bev);

	/* Copy all the data from the input buffer to the output buffer. */
	evbuffer_add_buffer(output, input);
}

static void
echo_event_cb(struct bufferevent *bev, short events, void *ctx)
{
	if (events & BEV_EVENT_ERROR)
		perror("Error from bufferevent");
	if (events & (BEV_EVENT_EOF | BEV_EVENT_ERROR)) {
		bufferevent_free(bev);
	}
}

static void
accept_conn_cb(struct evconnlistener *listener,
    evutil_socket_t fd, struct sockaddr *address, int socklen,
    void *ctx)
{
	/* We got a new connection! Set up a bufferevent for it. */
	struct event_base *base = evconnlistener_get_base(listener);
	struct bufferevent *bev = bufferevent_socket_new(
		base, fd, BEV_OPT_CLOSE_ON_FREE);

	bufferevent_setcb(bev, echo_read_cb, NULL, echo_event_cb, NULL);

	bufferevent_enable(bev, EV_READ|EV_WRITE);
}

static void
accept_error_cb(struct evconnlistener *listener, void *ctx)
{
	struct event_base *base = evconnlistener_get_base(listener);
	int err = EVUTIL_SOCKET_ERROR();
	fprintf(stderr, "Got an error %d (%s) on the listener. "
		"Shutting down.\n", err, evutil_socket_error_to_string(err));

	event_base_loopexit(base, NULL);
}

int
main(int argc, char **argv)
{
	struct event_base *base;
	struct evconnlistener *listener;
	struct sockaddr_in sin;

	int port = 9876;

	if (argc > 1) {
		port = atoi(argv[1]);
	}
	if (port<=0 || port>65535) {
		puts("Invalid port");
		return 1;
	}

	base = event_base_new();
	if (!base) {
		puts("Couldn't open event base");
		return 1;
	}

	/* Clear the sockaddr before using it, in case there are extra
	 * platform-specific fields that can mess us up. */
	memset(&sin, 0, sizeof(sin));
	/* This is an INET address */
	sin.sin_family = AF_INET;
	/* Listen on 0.0.0.0 */
	sin.sin_addr.s_addr = htonl(0);
	/* Listen on the given port. */
	sin.sin_port = htons(port);

	listener = evconnlistener_new_bind(base, accept_conn_cb, NULL,
	    LEV_OPT_CLOSE_ON_FREE|LEV_OPT_REUSEABLE, -1,
	    (struct sockaddr*)&sin, sizeof(sin));
	if (!listener) {
		perror("Couldn't create listener");
		return 1;
	}
        evconnlistener_set_error_cb(listener, accept_error_cb);

	event_base_dispatch(base);
	return 0;
}
